[MIPS] rbtx4938: Convert SPI codes to use generic SPI drivers
Use rtc-rs5c348 and at25 spi protocol driver and spi_txx9 spi
controller driver instead of platform dependent codes.
This patch also removes dependencies to old RTC interfaces such as
rtc_mips_get_time, etc.
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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